Instant snapshots from
SwiftUI #Previews

Prefire turns your #Preview blocks into snapshot tests, living docs & playbooks — automatically.

iOS playbook previews snapshot-testing Swift 6 SwiftUI tvOS UIKit Xcode Plugins iOS playbook previews snapshot-testing Swift 6 SwiftUI tvOS UIKit Xcode Plugins

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Why Prefire?

The fastest way to create snapshot tests and living documentation from your existing SwiftUI previews

📸

Zero Boilerplate

Snapshot tests from your #Preview blocks — no extra code needed.

📚

Living Docs

Documentation that's always in sync with your UI components.

⚡️

Ultra-Fast Caching

Smart cache system prevents redundant parsing and speeds up builds.

🧩

SwiftUI & UIKit

Works seamlessly with both SwiftUI and legacy UIKit codebases.

🔩

Flexible Integration

CLI, SPM plugin, Xcode plugin, or direct CI integration.

🧠

Flow Understanding

Track user stories, states, variants and complex UI flows.

Key Features

Everything you need for automated snapshot testing and visual documentation

🧠

Smart Preview Parsing

Understands #Preview, @Previewable, flows & variations automatically.

📸

Automatic Snapshots

Generates & executes pixel-perfect tests on every build automatically.

📚

Interactive Playbook

Beautiful browsable catalog for designers, QA, and stakeholders.

⚙️

CLI & CI Ready

Runs in CI/CD pipelines with zero configuration required.

Installation

Choose the method that fits your workflow best

Add Prefire via File → Add Packages…
Select your unit test target
Attach PrefireTestsPlugin under Build Tool Plugins
Build the target — snapshot tests are auto-generated

dependencies: [
    .package(url: "https://github.com/BarredEwe/Prefire", from: "4.0.0")
],
.testTarget(
    plugins: [
        .plugin(name: "PrefireTestsPlugin", package: "Prefire")
    ]
)

brew tap barredewe/prefire
brew install prefire

prefire tests
prefire playbook

Quick Start

Get up and running in less than 5 minutes

1
Add Prefire to your Package.swift (see Installation above)
2
Create a #Preview, e.g. #Preview { Button("Submit") }
3
Run the test target — Prefire will generate & run snapshot tests automatically

How Prefire Works

A deep dive into the architecture and workflow

Parse Source Files

Scans all Swift files, detecting #Preview blocks and PreviewProviders with modifiers like .prefireEnabled().

Cache Models

Fingerprints AST & preview bodies (SHA-256 + timestamps) to skip work on unchanged files.

Generate Tests

Uses Stencil templates & your .prefire.yml to emit Swift tests.

Build Playbook

Creates PreviewModels.generated.swift grouping previews by UserStory and State.

Internal Architecture

🔧
PrefireCore — AST parsing, preview detection & caching layer
⚡️
PrefireGenerator — Stencil-based code generator for tests & models
💾
PrefireCacheManager — Unified fingerprint & file-cache logic
🔌
Plugins — Xcode & SPM integration points
🛠
prefire CLI — Manual tests / playbook commands

Usage Examples

Real-world examples of Prefire in action

#Preview {
  Text("Hello")
}

#Preview {
  LoginView()
    .previewUserStory(.auth)
    .previewState(.loading)
    .snapshot(delay: 0.3, precision: 0.95)
}

Combine .previewUserStory(), .previewState() & .snapshot() to define rich visual flows & quality checks.

Configuration

Customize generation with .prefire.yml at your project root

📄 Show Example Configuration

test_configuration:
  target: MyApp
  test_file_path: Tests/Generated/PreviewTests.swift
  simulator_device: "iPhone15,2"
  preview_default_enabled: true
  sources:
    - {PROJECT_DIR}/Sources/
  snapshot_devices:
    - iPhone 14
    - iPad
  imports:
    - SwiftUI
    - UIKit
  testable_imports:
    - MyApp

playbook_configuration:
  template_file_path: Templates/PreviewModels.stencil
  preview_default_enabled: true

Open Source

Prefire is fully open source and built by the community. Contributions, issues and stars are always welcome!

View on GitHub

PRs, issues and feedback are highly appreciated — or just drop us a ⭐️!

Instant snapshots from SwiftUI #Previews